A request is made for funds to install a Coherent 50 mW 561 nm solid-state laser and upgrade a FACS Aria high-speed cell sorter at the Flow Cytometry and Cell Sorting (FCCS) facility at the University of Vermont. The FCCS Core facility in the College of Medicine houses the only cell sorter present at the University. Therefore, this single instrument must be able to serve the needs of all investigators at the University who require cell sorting for their research. Currently, this instrument supports 15 NIH-supported investigators and 27 NIH grants and is serving a broad community of investigators from a variety of disciplines. Both shifting emphases in research and the recruitment of new faculty have resulted in a number of investigators who need to sort cells expressing red fluorescent proteins, which are optimally excited by a 561 nm laser line. Since our current instrument does not possess this laser, these investigators cannot conduct their NIH-funded research. We have determined that we can meet the needs of our investigators by upgrading our current instrument so that a 561 nm laser can be installed. This upgrade is a fraction of the cost of the purchase of a new instrument. The upgraded instrument will remain located in the FCCS core, which has been in existence for over 20 years. This facility is managed by an experienced and accredited scientist/cytometrist, is directed by a faculty advisor with over 20 years of experience in flow cytometry, and is overseen by an internal advisory committee. In addition, the facility continues to enjoy strong institutional support from the University Of Vermont College Of Medicine.